Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 13. 1987. (Budapest, 1987)

P-T values of the amphibolites' first assemblages (6.8-7.9 kbar/517-525°C) correspond fairly well to those estimated with the help of WENKLER's isograde system. The intermediate values of metamorphic (thermal) gradients calculated bypiinear extrapolation of the depth-temperature relationship prove intermediate pressure (Barrovian) regional metamorphism (18-26°C/km). The first, prograde metamorphism was generally not followed by migmatitization in the area in question. However, coarse grained aggregates of microcline+plagioclase+quartz in blastomylonite (Kism-3. ) or the microcline content in samples Kaba-D-3. 1/A, Kaba-D-6. 3.) may indicate incipient anatexis. T °C 0 100 200 300 400 500 600 700 1 1 1 1 1 1 Fig. 5 P-T relations of the first (I) and second (II) metamorphic events in the surrounding of the Derecske Depression Legend: la= amphibolites, lb= gneiss (equilibrated after the thermal climax), in the (I) event, 2= amphibolites equilibrated (2a) or quasi-equilibrated (2b) in the (II) event, 3-4-5= arrows indicating the partly prograde, partly retrograde character of the overprint of low-pressure type. Al

2

Si0

5 triple point after HOLDAWAY (1971): A= andalusite, S= sillimanite, K= kyanite. Glaucophane and jadeite+quartz isogrades after WINKLER (1979) The tectonic and physical conditions, and consequently the mineral paragenetic and textural features of the second metamorphic event were strongly varying on a regional scale In the closest vicinity of the late-kinematic granite intrusion (Biharnagybajom) the matrix of the amphibolite sample No. Bi-20. 11. was equilibrated during the first metamorphic IS